The present disclosure is directed to inductors, and more specifically to immersion cooled inductors.
It is known in the art that inductors generate large amounts of heat during operation. In order to prevent damage due to overheating, inductors are cooled. One method of cooling an inductor is to immerse the inductor in a dielectric cooling liquid within a hermetically sealed cooling tank. This configuration is referred to as an immersion cooled inductor.
With high heat flux immersion cooling, heat from the inductor causes the dielectric cooling liquid to change states from a liquid to a gas (referred to as boiling). The heated cooling vapor (gas) rises to the top of the hermetically sealed cooling tank and condenses, thereby providing a cooling effect to the inductor. The rising gas is normally in a moving collection of bubbles, but other flow patterns such as annular flow are possible. Most commonly, the vapor is condensed in a heat exchanger which is cooled by another fluid, usually air. In some designs a submerged condenser is used as a part of the vessel side walls and removes heat directly from the liquid.
For boiling to occur on a surface, that surface must be raised above the saturation temperature defined by the vessel pressure. This temperature excess, called “overshoot” can result in thermal damage to the windings or the core. The overshoot is a function of the heat flux and surface condition.
The excess heat involved in bringing the dielectric cooling liquid above the saturation temperature can damage the inductor. Furthermore, when an event (such as vibration) causes the cooling liquid to begin boiling above the saturation temperature, the body of cooling liquid all begins to vaporize almost instantaneously resulting in a violent boiling effect causing a rapid pressurization. The rapid pressurization produces large transient forces that can damage the inductor, the mounting features or containment vessel.